Adsorption and Release Kinetics, Equilibrium, and Thermodynamic Studies of Hymexazol onto Diatomite

Pesticide sustained-release agents have advantages of low toxicity, high efficiency, and long duration. However, the sustained-release effects were not ideal, such as short release time and low release rate. The physical and chemical properties of diatomite are high stability, high porosity, and good sustained-release and controlled-release abilities. A series of diatomite-based pesticide sustained-release agents were prepared by adsorbing hymexazol onto diatomite. Kinetics, equilibrium, and thermodynamic studies for adsorption were carried out as well. It was found that the modified diatomite has a better adsorption effect for hymexazol, and the adsorption rate reached 16.64%. The equilibrium data followed with the Langmuir isotherm model, and the adsorption process was an endothermic process. Release results showed that the diatomite-based pesticide has a significant sustained-release effect. The sustained-release time reached more than 25 days, and the maximum release rate was above 70%. The experimental data was fitted into the Ritger-Peppas equation, and it was found that the release was controlled by the Fick diffusion mechanism. This confirmed the applicability of the modified diatomite as an efficient adsorption carrier for pesticide release.